R/utils.R

In ropensci/rdefra: Interact with the UK AIR Pollution Database from DEFRA

# Endpoint
ukair_url <- "http://uk-air.defra.gov.uk"

# Main API function
ukair_api <- function(url = ukair_url, path = "", query = "") {
  url_test <- httr::modify_url(url = url, path = path, query = query)
  resp <- gracefully_fail(url_test)
  return(resp)
}

# From
# https://community.rstudio.com/t/internet-resources-should-fail-gracefully/49199/12
gracefully_fail <- function(remote_file) {

  try_GET <- function(x, ...) {
    tryCatch(
      httr::GET(url = x, httr::timeout(600), ...),
      error = function(e) conditionMessage(e),
      warning = function(w) conditionMessage(w)
    )
  }

  is_response <- function(x) {
    class(x) == "response"
  }

  # First check internet connection
  if (!curl::has_internet()) {
    message("No internet connection.")
    return(invisible(NULL))
  }

  # Then try for timeout problems
  resp <- try_GET(remote_file)
  if (!is_response(resp)) {
    message(resp)
    return(invisible(NULL))
  }

  # Then stop if status > 400
  if (httr::http_error(resp)) {
    httr::message_for_status(resp)
    return(invisible(NULL))
  }

  return(resp)

}